Pump system comprising a hydraulic pump, particularly for a steering system

ABSTRACT

A pump system with a hydraulic pump has a control element, which affects the pump output and to which control signals of a regulating and control unit can be supplied for adjustments.  
     Input signals, which represent the state variables and operational variables of a consumer and/or of a dynamic system, in which the consumer is integrated, are supplied to the regulating and control unit. The control signals can be generated in accordance with a functional relationship, which is stored in the regulating and control unit, as a function of the input signals and supplied to the control element.

[0001] The invention relates to a pump system with a hydraulic pump, especially for a steering system, as defined in the introductory portion of claim 1.

[0002] In the DE 34 20 519 A1 publication, a radical piston pump is described, which comprises a drivable rotor with radial boreholes, in which the pistons of the pump, which are mounted at the inside of an embracing curve ring, which is mounted eccentrically with respect to the rotor, are disposed. When the rotor rotates, a majority of pump pistons, uniformly distributed over the periphery, are pushed for a greater or lesser distance radially into their accommodating radical boreholes in the rotor, depending upon their actual position. The pump pistons act upon a fluid-accommodating space, the fluid being sucked into the space or expelled from it depending on the position of the pump piston. In this way, fluid can be pumped at an approximately constant rate.

[0003] For adjusting the flow rate and/or the pressure of the fluid flowing, an electrohydraulic pressure regulator is provided, which comprises a control piston, which adjusts to the position of the outer curve ring and is adjusted as a function of a control voltage supplied to a proportional magnet.

[0004] This known, controllable hydraulic pump is distinguished by a complicated construction and a high consumption of energy. Moreover, this pump has a poor response behavior, the delayed response times leading to inaccurate adjustments of the flow rate and the fluid pressure.

[0005] It is therefore an object of the invention to indicate a pump system, which can be adjusted precisely and is distinguished by a good response behavior and, at the same time, a simple construction. The pump system advisably is to be attainable as a manually variable system and, while in the running state, is to be adjustable to different external load requirements.

[0006] Pursuant to the invention, this objective is accomplished with the distinguishing features of claim 1. Advantageous further developments of the inventive object can be inferred from the dependant claims.

[0007] The inventive pump system comprises, on the one hand, a hydraulic pump for pumping hydraulic fluid to a consumer and, on the other, a control and/or regulating unit, in which control signals, which can be supplied to a control element of the pump for adjusting the output of the pump, can be generated as a function of measurement signals or other input signals. The regulating and control unit advantageously forms a unit, which is constructed separately from the pump and in which state variables and operational variables of the consumer, to which the hydraulic fluid is supplied as working medium, are supplied as input signals. In addition or alternatively to the state variables and operational variables of the consumer, it is also possible to take into consideration appropriate parameters of a dynamic system, in which the consumer is embedded and within which, the consumer forms a sub-system. In the regulating and control unit, control signals, which are supplied to the control element of the hydraulic pump for the current adjustment of the pump output, are generated from the input signals supplied in accordance with calculation specifications filed as characteristics or stored as a mathematical relationship.

[0008] This pump system is particularly suitable for use in a steering system for steering the wheels of a motor vehicle, the steering system representing the consumer, which is supplied with hydraulic fluid by the hydraulic pump, and the motor vehicle represents the subordinate, dynamic system, the state of which can be taken into consideration for the adjustment of the pump.

[0009] This pump system offers the advantage of a high variability, since the pump, output can be adjusted, using the signals of the regulating and control unit, directly to the requirements of the consumer. Particularly when used in steering systems in motor vehicles, this enables parameterizable pumps to be realized in steering systems, the output of which can be adjusted by state variables and system parameters, such as the vehicle speed, the steering angle speed an/or the yawing rate. A further advantage lies therein that, in the event that the system is in a stationary or quasi stationary state, it is possible to realize a comparatively small energy consumption can be realized.

[0010] Advantageously, a variable displacement pump is used, which is constructed as a vane type pump, roller vane pump or as radial piston pump. The variable displacement pump has a rotor with radial boreholes, which is mounted rotatably in a curve ring and driven by a motor, and pump elements, which can be displaced radially in the radial boreholes, supported with respect to the inside of the curve ring and act upon the fluid accommodation space. The relative position of the curve ring to the rotor can be adjusted by the control element between a concentric position and an eccentric position. For this construction, the pump output is varied by means of control signals of the regulating and control unit by means of an adjustment of the position of the curve ring relative to that of the rotor, which is brought about by the control element. State variables and operational variables of the consumer, especially of the steering system, and/or of the imposed dynamic system, especially of the motor vehicle, are converted directly into a change in the position of the curve ring relative to the rotor, so that the flow, which is pumped by the hydraulic pump, can be adapted basically exclusively by changing the geometry of the pump to the current requirement of the consumer. Orifice or bypass systems for regulating the flow can admittedly be combined in an advantageous manner with the adjustment of the pump geometry, but are not necessarily required.

[0011] Advisably, the position of the outer curve ring, embracing the rotor, can be adjusted by a control element, which is constructed as an electric motor. Adjustment of the outer curve ring by electric motor offers the advantage that very short response times can be realized, in order to be able to adjust the output to the current requirements. Reaction times as low as about 10 ms can be realized.

[0012] A further advantage consists therein that the electric motor can be controlled very precisely and small correcting paths, which are, however, associated with large forces can also be transposed. Optionally, it may be appropriate here to provide a reduction gear between the electric motor and the curve ring in order to be able to realize the required, short correcting paths and high correcting forces even with relatively small electric motors.

[0013] Since the pump and the electric motor, acting on the curve ring, form components, which function basically independently, a higher degree of flexibility is achieved, which comes about especially owing to the fact that only the transfer of motion from the rotor of the electric motor to the curve ring must be assured; additional supporting elements at the curve ring are therefore not necessarily required. Moreover, it is easier to supply current to the electric motor than to supply hydraulic fluid to the control systems known from the state of the art.

[0014] To adjust the position of the curve ring, the rotor of the electric motor is connected advantageously with an eccentric disk, which transfers the required controlling motion either directly from the rotor of the electric motor to the curve ring or indirectly oven an interposed transfer lever. If direct transfer is provided, the interposed transfer lever should advisably be shifted translationally, the displacement motion being produced in that an end of the transfer lever is acted upon by a cam plate at the eccentric disk. The indirect transfer with interposing the transfer lever offers the advantage that, because of the spatial separation of pump and electric motor, there is a plurality of possibilities for arranging the electric motor relative to the pump.

[0015] On the other hand, it is also possible for the eccentric disk to engage the curve ring directly, this version being distinguished by an especially compact construction, since it is possible to do without an interposed transfer linkage, so that frictional losses can be minimized.

[0016] Advisably, the pump is controlled by a closed-loop control circuit, which comprises a sensor for measuring an actual quantity, which corresponds to the pumping rate or pumping pressure of the pump, and, moreover, a regulating and control unit for comparing the magnitude of an actual value with a nominal value, which is stored or can be determined, as well as the value of the electric current for the electric motor, which is derived from the comparison of the nominal value with the actual value. The sensor advantageously is constructed here as a position sensor for determining the position of the curve ring, which can be used as a measure of the pumping pressure or pumping rate, since the pump output is determined by the extent of the deflection of the curve ring from a central or symmetrical position in relation to the rotor of the pump.

[0017] As sensor for determining the position of the curve ring, a magnetoresitive sensor, for example, may be used, which measures the magnetic field of a permanent magnet, which is disposed at the rotor of the electric motor or at a component, which is acted upon by the rotor. By these means, the magnetic field of the permanent magnet is altered in relation to the position sensor when the electric motor is actuated, this change in the magnetic field being measured and used as a measure of the positional change.

[0018] Ann example of the invention is described in greater detail below by means of the drawings, in which

[0019]FIG. 1 shows a diagrammatic representation of a vane-type pump for pumping a hydraulic fluid from a hydraulic reservoir to a consumer, a curve ring of the radial piston pump, influencing the pump output, being adjustable by means of an electric motor,

[0020]FIG. 2 shows a diagrammatic representation of a vane-type pump with an electric motor with an eccentric disk, the rotational motion of which can be converted into a linear, translational transfer motion of a transfer lever,

[0021]FIG. 3 shows a representation, corresponding to that of FIG. 2, however with an eccentric disk, which is integrated in the curve ring and driven by the rotor of the electric motor,

[0022]FIG. 4 shows a magnetoresistive position sensor, which interacts with a permanent magnet, which is disposed on the eccentric disk and

[0023]FIG. 5 shows a diagrammatic view of a control circuit for adjusting the electric motor.

[0024] In the following Figures, identical components have identical reference numbers.

[0025] In FIG. 1, a vane-type pump 1 is shown, which aspirates hydraulic fluid from a hydraulic reservoir 3 by way of a first conveying pipeline 2 and pumps it over a second conveying pipeline 4 at an elevated pressure to a consumer 5. The consumer 5 is a steering system, especially one which can be actuated a hydraulically, in a motor vehicle. A return pipeline 6, which leads back to the hydraulic reservoir 3, branches off from the conveying pipeline 4. A safety valve 7 is integrated into the hydraulic pipeline 6 and, when a maximum pressure is exceeded, is shifted into the open position, so that hydraulic fluid can flow back from the conveying pipeline 4 over the return pipeline 6 into the hydraulic reservoir 3. Usually, the safety valve 7 opens up only at a maximum pressure, which, as a rule, is clearly higher than the pumping pressure supplied to the consumer 5.

[0026] The vane-type pump 1 comprises a rotor 8, which is mounted rotatably in a housing, the details of which are not shown, and which is embraced by a curve ring 9. The rotor 8 is driven by a driving unit, such as an internal combustion engine. The rotor 8 has radial guides 10, which are distributed uniformly over its periphery and in which pump elements, constructed as displacing elements, are taken up radially displaceably. The displacing elements 11 are supported at the inside of the curve ring 9. The radial guides 10 communicate with a fluid accommodating space for pumping hydraulic fluid, a radial movement of the radial piston 11 in the radial boreholes 10 producing a suction and pumping pressure, which aspirates be hydraulic fluid from the hydraulic reservoir 3 and pumps it in the direction of the consumer 5.

[0027] The pump 1 is constructed as a variable displacement pump with variable pump geometry. For this purpose, the position of the curve ring 9 with respect to the rotor 8 can be adjusted infinitely variably between a concentric position and a maximum eccentric position, in which the rotor 8 lies in a direct contact with the inside of the curve ring 9. The pumping output of the radial piston pump 1 is determined by the extent of the eccentric deflection of the curve ring 9 with respect to the rotor 8.

[0028] The curve ring 9 is mounted so that it can rotate about a pivot point 12. On the side radially opposite to the pivot point 12, the curve ring 9 engages a control elements 13, which is constructed as an electric motor 14 and the controlling movement of which, which is to be transferred to the curve ring 9, is converted into a swiveling motion about its pivot point 12 in the direction of arrow 15, as a result of which the curve ring is adjusted infinitely variably between its concentric position and the maximum eccentric position. The transfer of the controlling motion of the electric motor 14 to the curve ring 9 is accomplished advisably over a transfer lever 16, which can be moved translationally, is acted upon by the rotor of the electric motor and engages the curve ring 9 tangentially.

[0029] Instead of an electric motor as control element for changing the position of the curve ring relative to the rotor, it may also be appropriate to use a lifting magnet. Furthermore, it may be appropriate to bring about the adjustment hydraulically.

[0030] Control signals S_(Stell), which generally are produced in a regulating and control unit 18, are supplied to the electric motor 14 for adjustments over signal leads. The control signals S_(Stell) are generated in accordance with a relationship, deposited as characteristics or as a calculating formula in the regulating and control unit 18, as a function of input signals S_(Ein), which represent state variables and operational variables of the pump 1, the consumer 5 and optionally other components, especially an internal combustion engine.

[0031] The pump geometry is affected by the change in the position of the curve ring relative to the rotor. This has an effect on the power P supplied to the consumer, the effect being calculated from the equation

P=V _(Geom) ×n×p

[0032] in which V_(Geom) is a characteristic value for the pump geometry, which depends on the position of the curve ring relative to the rotor, n is the rpm of the rotor and p is the pressure of the hydraulic fluid supplied to the consumer. Since the rpm of the rotor and therefore also the pump output depend on the rpm of the internal combustion engine when the latter is the driving unit, a pump control, which is independent of the rpm and for which advisably the pump geometry is manipulated, is required for achieving a constant pump output. The pump geometry is also adjusted for adapting it to the actual requirements of the consumer by acting upon the curve ring by way of the electric motor.

[0033] In addition to or instead of manipulating the pump geometry, the output P, supplied to the consumer, can also be varied by varying the pressure p supplied to the consumer, for example, by a variably adjustable orifice in pipeline 4 conveying hydraulic fluid to the consumer.

[0034]FIG. 2 shows the radial piston pump 1 in an enlarged, diagrammatic representation. The rotor 19 of the electric motor 14 is connected with an eccentric disk 20, which is rotated by the electric motor. The translationally displaceable transfer lever 16 lies in contact with the peripheral surface of the eccentric disk 20. The peripheral surface of the eccentric disk 20 forms a cam plate for the transfer lever 16, so that the actual position of the transfer lever is determined by the actual rotational position of the eccentric disk 20. The end of the transfer lever 16, lying opposite the eccentric disk 20, tangentially engages the side of the curve ring 9, lying radially opposite the pivot point 12, and rotates this curve ring 9 about its pivot point 12 in the direction of arrow 15.

[0035] Furthermore, an inlet opening 21, over which hydraulic fluid is supplied from the hydraulic reservoir of the pump 1, and a pressure outlet opening 22, through which the hydraulic fluid under pressure is supplied to the consumer, are drawn in FIG. 2.

[0036] The representation of FIG. 3 corresponds to that of FIG. 2 with the difference that the transfer of the control motion of the electric motor 14 is accomplished directly on the curve ring 9 without interposing a transfer element. For this purpose, the eccentric disk 20, disposed at the rotor 19 of the electric motor, is taken up in a corresponding eccentric seat 23 on the outside of the curve ring 9. During a twisting of the rotor 19 and of the eccentric disk 20, the outside of the eccentric disk 20 acts on assigned wall sections of the eccentric seat 23 and, by these means, brings about an adjusting force acting on the curve ring 9 in the direction of arrow 15 and twisting the curve ring 9 about is pivot point 12.

[0037] In order to be able operate pump 1 in a closed control circuit and to adjust the pump output to a desired level, the actual position of the curve ring in relation to the rotor must be determined by a sensor. For this purpose, a position sensor 24, shown in FIG. 4, is provided. Advantageously, it is constructed magnetoresistively and interacts with a permanent magnet 25, which advisably is disposed on the end face of the eccentric disk 20. The magnetoresistive position sensor 24 is in a position to measure the magnetic field produced by the permanent magnet 25. Because of the eccentric arrangement of the eccentric disk 20, a magnetic field, which depends on the actual rotational position of the eccentric disk 20 and from which the rotational position can be derived, is sensed by the position sensor 24. Since the eccentric disk 20 and the curve ring 9 are coupled kinematically, the position of the curve ring 9 can also be concluded from the position of the eccentric disk 20.

[0038] Optionally, it may also be appropriate to measure the actual position of the curve ring 9 directly, for example, by fastening a permanent magnet on the outside of the curve ring 9 and sensing using a magnetoresistive position sensor.

[0039] Advantageously, the position sensor 24 is held in stationary fashion on a printed circuit board 26, on which additional evaluating components 27 for evaluating the measurement signals of the position sensor 24 are disposed.

[0040] It can furthermore be inferred from FIG. 4 that a reduction gear may be provided at the electric motor 14, in order to convert the rotation of the electric motor into a smaller rotation with, however, a higher torque.

[0041]FIG. 5 shows a closed control circuit, which can be realized particularly in a regulating and control unit 18, for adjusting the electric motor 14 and, with that, the curve ring of the pump and the pumping output of the pump. The actual value of the eccentric disk or of the curve ring or a value, such as the pumping rate or pressure, which is correlated with the position of the curve ring, is determined by way of the position sensor 24. The value measured is supplied as input signal S_(Ein) to a sensor pre-amplifier 29, in which the signal is amplified. The amplified signal is supplied to a controller 30, which comprises an analog-digital converter 31 for converting the amplified measurement signal into a digital value, a controller 32 and a pulse-width modulator 33. Furthermore, a CAN bus 34, for transmitting vehicle signals to the controller 30, as well as a calibration memory 35, for calibrating the sensor 24, are assigned to the controller 30. The function of the various sub-units of the controller 30 is controlled and coordinated by software 36.

[0042] The pulse-width modulated signal, generated in the controller 30, is amplified in a final stage 37 and supplied to the electric motor 14 as a control signal S_(Stell) for the adjustment of the latter.

[0043] The pump system, described above, is also suitable for use in transmission systems, such as lubricating-cooling-switching pumps, or also in other applications in motor vehicles, such as valve controls in internal combustion engines, power brakes, etc. 

1. Pump system with a hydraulic pump, especially for a steering system for steering the wheels of a motor vehicle, with a control element (13) which affects the output of the pump and to which control signals (S_(Stell)) of a regulating and control unit (18) can be supplied for adjustments, characterized in that input signals (S_(Ein)), which represent state variables and operational variables of a consumer (5) and/or of a dynamic system, in which the consumer (5) is integrated, can be supplied to the regulating and control unit (18), and in that the control signals (S_(Stell)) can be generated in accordance with a functional relationship, which is stored in the regulating and control unit, as a function of the input signals (S_(Ein)) and supplied to the control element (13).
 2. The pump system of clam 1, characterized in that the control element (13) is an electric motor (14).
 3. The pump system of claims 1 or 2, characterized in that the control element (13) is an electric lifting magnet.
 4. The pump system of one of the claims 1 to 3, characterized in that an adjustable orifice is provided in a fluid pipeline from the pump (1) to the consumer (5) and can be adjusted by control signals (S_(Stell)) of the regulating and control unit (18).
 5. The pumps system of clam 4, characterized in that the pressure gradient ever the office can be used to adjust the pump (1).
 6. Pump system for a steering system of one of the claims 1 to 5, characterized in that the speed (v) of the vehicle, the steering angle speed and/or the yawing rate or other vehicle system signals can be used as state variables and operational variables and supplied to the regulating and control unit (18) as input signals (S_(Ein)).
 7. The pump system of one of the claims 1 to 6, characterized in that a closed control circuit is provided for adjusting an electric current, acting on the control element (13), the control circuit comprising a sensor (24) for measuring an actual quantity, which correlates with the pumping rate and/or the pumping pressure, and a controller (32) for comparing an actual quantity with a value for the electric current derived therefrom.
 8. The pump system of one of the claims 1 to 7, characterized in that a vane-type pump or a roller vane pump or a radial piston pump is used as pump, which is constructed as an adjusting pump and has a rotor (8), which is rotatably mounted within a curve ring (9) and a driven by a motor, with radial boreholes (10), in which there are radially displaceable pump elements, which can be supported opposite the inside of the curve ring, which pump elements act upon a fluid-accommodation space, the position of the curve ring (9) relative to the rotor (8) being adjustable by the control element (13) between a concentric position and an eccentric position.
 9. The pump system of claim 8, characterized in that the curve ring (9) can be adjusted relative to the rotor (8).
 10. The pump system of claims 8 or 9, characterized in that the control element (13) drives an eccentric disk (20), the movement of which can be transferred to the curve ring of (9).
 11. The pump system of claim 10, characterized in that a translationally movable transfer lever (16) is provided between the eccentric disk (20) and the curve ring (9).
 12. The pump system of claim 10, characterized in that the eccentric disk (20) engages the curve ring (9) directly.
 13. The pump system of one of the claims 8 to 12, characterized in that the curve ring (9) is mounted so that it can rotate about a pivot point (12) and engages the control element (13) at the curve ring (9) at a distance from the pivot point (12).
 14. The pump system of one of the claims 8 to 13, characterized in that a position sensor (24) is provided for determining the position of the curve ring (9) or a quantity correlating therewith and in that the electric current, acting upon the control element (13), can be adjusted as a function of the measurement signals of the position sensor (24).
 15. The pump system of claim 14, characterized in that the position sensor (24) is constructed to be magnetoresistive, the actual position of the rotor (19) or of the component, acted upon by the latter, being determined by measuring the magnetic field of a permanent magnet (25), which is disposed at the control element (13) or at a component acted upon by the latter.
 16. The pump system of one of the claims 1 to 15, characterized in that a reduction gear (28) is provided between the control element (13) and the adjustable curve ring (9). 